© The Associated Press
A group of federal police stand in front of the prison in Piedras Negras, Mexico, after a mass escape by inmates
Mexico City - More than 130 inmates escaped through a tunnel from a Mexican prison on the border with the United States in one of the worst jailbreaks the country's beleaguered penal system has suffered in recent years.

Homero Ramos, attorney general of the northern state of Coahuila, said 132 inmates of the prison in the city of Piedras Negras had got out through the tunnel in an old carpentry workshop, then cut the wire surrounding the complex.

Corrupt prison officials may have helped the inmates escape, said Jorge Luis Moran, chief of public security in Coahuila, adding that U.S. authorities had been alerted to help capture the fugitives if they try to cross the border.

The jailbreak is a reminder of the challenges that await Enrique Pena Nieto, the incoming president, who has pledged to reduce crime in the country after six years of increased gang-related violence under President Felipe Calderon.

Many of Mexico's prisons are overcrowded and struggle to counter the influence of criminal gangs that can use their financial muscle to corrupt those in charge.

Ramos said that the state government of Coahuila was offering a reward of 200,000 pesos ($15,700) for information leading to the capture of each fugitive.

The Piedras Negras complex housed a total of 734 inmates, and the tunnel through which the prisoners escaped was about 1.2 meters (four feet) wide, 2.9 meters (9-1/2 feet) deep and seven meters (23 feet) long, Ramos said.

Mass Breakouts

There have been numerous mass breakouts in the last few years from Mexico's penal system, and prison officials are frequently accused of complicity with drug cartels.

At the end of 2010, more than 140 inmates escaped a prison in the border city of Nuevo Laredo. This February, at least 44 people died in a fight between rival gangs at an overcrowded prison in northern Mexico.

Pena Nieto has pledged to reform the prisons, though experts say he will struggle to make an impact unless he combines this with root-and-branch reform of the justice system.

Pena Nieto, 46, of the centrist Institutional Revolutionary Party (PRI), will take office in December. The PRI was widely accused of corruption during its long rule between 1929-2000, and he has promised to break with that checkered past.

Northern Mexico has been hit particularly hard by violence stemming from brutal turf wars between drug gangs that have overshadowed Calderon's conservative administration.

Calderon has used the military to try and crack down on the gangs, and has captured or killed many of the top drug lords.

But his efforts have come at a price.

Gang-related violence has surged on Calderon's watch, and fighting between cartels and their clashes with security forces have claimed more than 55,000 lives over the past six years.

Last week the Mexican Navy captured one of the biggest kingpins active near the U.S.-Mexican border, the leader of the Gulf Cartel, Jorge Costilla, known as "El Coss."

Analysts forecast this would lead to an increase in criminal activity in northern Mexico as rival gangs fought for control of lucrative smuggling routes in the area. ($1 = 12.7486 Mexican pesos)

Source: Reuters; reporting by Lizbeth Diaz and Armando Tovar; Writing by Dave Graham